Automobile seats are made using foam padding of different density and compressibility depending on factors such as cost and level of sportiness/luxury. The foam used for seats in sports cars will typically be relatively hard and relatively thin, in order to provide a high level of support, in particular lateral support. In seats for sporty automobiles, the foam is attached to a hard shell which will typically include deep supports either side of the seat cushion to restrain lateral movement of the legs/hips and additional deep supports either side of the backrest to restrain lateral movement of the body. On the other hand, at the luxury end of the market, the supports either side of the seat cushion are relatively shallow and formed by the shape of the cushion itself, to make it easier to get into and out of the seat, similarly the bolsters either side of the backrest are shallow, to aid entry/exit. The foam padding of seat cushions and backrests in luxury automobiles tend to be soft and thick to provide a high degree of cushioning and comfort. In between these two market segments, a compromise between hard, thin foams and soft thick foams is made to provide sufficient comfort at an acceptable cost.
Seats have been proposed in which a plurality of foams of different hardness are provided. For example, JP2010-142571 and US2010/0133891 both disclose seats in which the seat cushion has a hard lower layer (which is generally cheaper to produce) and a soft upper layer for comfort. FR2942423 on the other hand discloses seat padding, in which rather than providing bolsters as a hard shell covered with foam, bolsters are formed from a hard foam formed in a mould alongside a central region of softer foam.
The present invention is concerned especially with the provision of seats for luxury automobiles, in which a high level of softness is required for comfort alongside an aesthetically pleasing appearance. A high level of softness can be obtained by use of thick, soft foam as discussed above, however, when upholstery is applied to thick layers of soft foam, tension in the trimming materials e.g. leather upholstery, around the outer edge of the foam can crush and crease the foam giving visually unacceptable results, including “gapping”, where a gap can be seen beneath the upholstery, where the foam is not applying outward pressure on the upholstery. This leads to a perceivable air gap between the upholstery and the foam beneath. These creases/gaps in backrests can reduce the lateral support and comfort of a seat.
Embodiments of the present invention seek to overcome this problem without sacrificing the comfort associated with soft foam padding.